#48 - Add release notes to Femah.Core NuGet package when publishing.

- Added the Update-ReleaseNotesFromGithub task to the Commit build, this programatically retrieves the matching Release from Github for the current [major].[minor] build and updates the <releaseNotes></releaseNotes> element within the .nuspec file prior to packaging the NuGet and Symbolsource packages. Try it by doing .\Start-Build.bat as usual.